package com.sheep.jucdemo.part6.part6_2;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.AbstractQueuedSynchronizer;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;

/**
 * @Date 2022/4/24 20:51
 * @Created by sheep
 */
public class Test6_2_3_1 implements Lock, java.io.Serializable {

    private final Sync sync = new Sync();

    @Override
    public void lock() {
        sync.acquire(1);
    }

    @Override
    public boolean tryLock() {
        return sync.tryAcquire(1);
    }

    @Override
    public void unlock() {
        sync.release(1);
    }

    @Override
    public Condition newCondition() {
        return sync.newCondition();
    }

    public boolean isLocked(){
        return sync.isHeldExclusively();
    }

    @Override
    public void lockInterruptibly() throws InterruptedException {
        sync.acquireSharedInterruptibly(1);
    }

    @Override
    public boolean tryLock(long timeout, TimeUnit unit) throws InterruptedException {
        return sync.tryAcquireNanos(1,unit.toNanos(timeout));
    }

    // 内部帮助类
    private static class Sync extends AbstractQueuedSynchronizer{
        @Override
        protected boolean tryAcquire(int arg) {
            //assert acquires == 1;
            if (compareAndSetState(0,1)){
                setExclusiveOwnerThread(Thread.currentThread());
                return true;
            }
            return false;
        }

        @Override
        protected boolean tryRelease(int arg) {
            //assert release == 1;
            if (getState() == 0){
                throw new IllegalMonitorStateException();
            }
            setExclusiveOwnerThread(null);
            setState(0);
            return true;
        }

        @Override
        protected boolean isHeldExclusively() {
            return getState() == 1;
        }

        Condition newCondition(){
            return new ConditionObject();
        }
    }

}
